package 牛客;

import java.util.Scanner;

/**
 * @Auther: zhang l
 * @Date: 2022/4/12 - 04 - 12 - 9:53
 * @Description: 牛客
 * @version: 1.0
 */
public class 求平均数 {
    public static void main(String[] args) {
        Scanner scan=new Scanner(System.in);
        int count =0;
        double ave=0;
        double avg=0.00;
        while (true){
            int a=scan.nextInt();
            if (a<0){
                break;
            }
            count++;
            ave+=a;
        }
      avg=ave/count;
        System.out.println(String.format("%.2f",avg));
    }
}
